An assessment of the invasive status of Berberis aristata and B. julianae in South Africa

An assessment of the invasive status of Berberis aristata and B. julianae in South AfricaJan-Hendrik Keet1,2, Dan’sile Cindi1, Johann du Preez21Invasive Species Programme, SANBI; 2University of the Free State

The genus Berberis (Berberidaceae), commonly called barberry, contains approximately 500 species. Berberis species have been distributed all over the world for their horticultural uses, the most popular of which is in the landscaping industry. This has resulted in several species escaping from cultivation and becoming invasive in some parts of the world, including South Africa. Invasive Berberis can have considerable negative environmental and economic impacts, such as altering soil chemistry, lowering veld carrying capacity, preventing access to watercourses when occurring in dense stands, and replacing indigenous vegetation. Several species also serve as alternate hosts for the destructive black stem rust disease of wheat. No formal study has been conducted regarding the history, invasive status or impact of Berberis in South Africa and the aim of this study is to assess the invasion potential of species that have started to naturalize. This study so far has led to the detection of naturalized populations of B. julianae in Golden Gate Highlands National Park (Free State) and B. aristata in the Woodbush State Forest (Limpopo Province). The main population of B. julianae in Golden Gate has approximately 380 individuals while that of B. aristata in Woodbush has approximately 5 500 individuals. Results that will be discussed include seed viability tests conducted on B. julianae, bioclimatic analysis for B. julianae and B. aristata, and weed risk assessments. The research aims to determine whether these Berberis species should be listed in NEMBA as category 1a invaders.